diff --git a/object.js b/object.js
index b2ab737..47351c0 100755
--- a/object.js
+++ b/object.js
@@ -1027,9 +1027,17 @@ Object.assign(Constructor, {
 
 // Mix a set of methods/props/attrs into an object...
 // 
+//	Mix objects into base...
 //	mixinFlat(base, object, ...)
 //		-> base
 //
+//	Soft mix objects into base...
+//	mixinFlat('soft', base, object, ...)
+//		-> base
+//
+//
+// 'soft' mode only mixies in props if base does not define them already
+//
 //
 // NOTE: essentially this is just like Object.assign(..) but copies 
 // 		properties directly rather than copying property values...
@@ -1040,12 +1048,19 @@ Object.assign(Constructor, {
 var mixinFlat = 
 module.mixinFlat = 
 function(base, ...objects){
+	var soft = base === 'soft'
+	if(soft){
+		base = objects.shift() 
+		objects = objects
+			.slice()
+			.reverse() }
 	return objects
 		.reduce(function(base, cur){
 			Object.keys(cur)
 				.map(function(k){
-					Object.defineProperty(base, k,
-						Object.getOwnPropertyDescriptor(cur, k)) })
+					;(!soft || !base.hasOwnProperty(k))
+						&& Object.defineProperty(base, k,
+							Object.getOwnPropertyDescriptor(cur, k)) })
 			return base }, base) }
 
 
@@ -1258,6 +1273,7 @@ Constructor('Mixin', {
 	// This can be:
 	// 	'proto'		- mix data into prototype chain (default)
 	// 	'flat'		- use mixinFlat(..) to copy data
+	// 	'softflat'	- like 'flat' but uses mixinFlat('soft', ..)
 	mode: 'proto',
 
 	// base API...
@@ -1272,7 +1288,9 @@ Constructor('Mixin', {
 		typeof(target) == typeof('str')
 			&& ([_, mode, target] = arguments)
 		return mode == 'flat' ?
-			this.constructor.mixinFlat(target, this.data)
+				this.constructor.mixinFlat(target, this.data)
+			: mode == 'softflat' ?
+				this.constructor.mixinFlat('soft', target, this.data)
 			: this.constructor.mixin(target, this.data) },
 
 	__init__: function(name, ...data){
diff --git a/package.json b/package.json
index abcacb9..9d08e02 100755
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "ig-object",
-  "version": "5.4.9",
+  "version": "5.4.10",
   "description": "",
   "main": "object.js",
   "scripts": {
diff --git a/test.js b/test.js
index 90ce9db..0bba893 100755
--- a/test.js
+++ b/test.js
@@ -760,6 +760,12 @@ var cases = test.Cases({
 		assert('b' in x == false, 'post-mixout content gone')
 		assert('c' in x == false, 'post-mixout content gone')
 
+		var z = assert(C('softflat', {a:'zzz'}), `C("flat", {})`)
+
+		assert(z.a == 'zzz', 'no overwrite')
+		assert(z.b == 'bbb', 'mixin content from C')
+		assert(z.c == 'ccc', 'mixin content from C')
+
 	},
 })